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HINTS
AND TIPS
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| STARTING
from cold. Flood the carburetter by depressing the tickler,
and close the air valve, Then open the throttle a little, eg:
about one eighth open, see diagram on sheet
7 position 2, then kick-start. If it is too much open starting
will be difficult. When engine starts open air valve and close
the throttle; if the engine begins to falter, partially close
the air valve until the engine is warm, then set in the fully
open position. |
| STARTING,
engine hot. Do not flood the carburetter, Then open the
throttle about one eighth of its travel and kick-start. If the
carburetter has been flooded and won't start because the mixture
is too rich - open the throttle wide and give the engine several
turns to clear the richness, then start again with the throttle
one eighth open, and air lever wide open. Generally speaking
it is not advisable to flood at all when an engine is hot. |
| STARTING,
general. By experiment, find out if and when it is necessary
to flood, also note the best position for the air lever and
the throttle for the easiest starting. |
CABLE CONTROLS. See that there is a minimum of backlash
when the controls are set back and that any movement of the
handlebar does not cause the throttle to open; this is done
by the adjusters on the top of the carburetter. See that the
throttle shuts down freely. |
PETROL FEED, verification. Later models are fitted
with a filter gauze at the inlet to the float chamber. To remove
the filter gauze, unscrew the banjo bolt (22), the banjo can
then be removed and the filter gauze removed from the needle
seating. Ensure that the filter gauze is not damaged and free
from dirt. Before replacing the banjo, turn on the petrol tap
momentarily and see that the fuel gushes out. Avoid petrol pipes
with vertical loops as they cause air locks. Flooding
may be due to a worn or bent needle or a leaky float, but nearly
all flooding with new machines is due to impurities (grit, fluff
etc.) in the tank, so clean out the float chamber periodically
until the trouble ceases. If the trouble persists, the tank
might be drained, swilled out, etc. |
FIXING
CARBURETTER AND AIR LEAKS. Erratic
slow running is often caused by air leaks, so verify there are
none at the point of attachment to the cylinder or inlet pipe,
check by means of an oil can and eliminate by new washers and
the equal tightening up of the flange nuts. Most models have
an "O" ring provision machined into the flange, make
sure that this is undamaged and replace if necessary.Also in
old machines look out for air leaks caused by a worn throttle
or worn inlet valve guides. |
BANGING IN EXHAUST may be caused by too weak a pilot
mixture when the throttle is closed, it may also be caused by
too rich a pilot mixture and an air leak in the exhaust system,
the reason in either case is that the mixture has not fired
in the cylinder and has fired in the hot silencer. If the banging
happens when the throttle is fairly wide open, the trouble will
be ignition not carburation. |
BAD PETROL CONSUMPTION of a new machine may be due to
flooding, caused by impurities from the petrol tank lodging
on the float needle seat and so prevent its valve from closing.
If the machine has had several years use, flooding may be caused
by a worn float needle valve. Also bad petrol consumption will
be apparent if the throttle needle jet "15" (see fig.
2 sheet 2) has
worn; it may be remedied or improved by lowering the needle
in the throttle, but if it cannot be then the only remedy is
to get a new needle jet. |
AIR FILTERS. These may affect the jet setting, so if
one is fitted afterwards to the carburetter the main jet may
have to be smaller. If a carburetter is set with an air filter
and the engine is to run without it, take care not to overheat
the engine due to too weak a mixture; testing with the air valve
(sheet 5) will
indicate if a larger main jet and higher needle position are
required. |
EFFECT OF ALTITUDE ON CARBURETTER. Increased altitude
tends to produce a rich mixture. The greater the altitude, the
smaller the main jet required. Carburetters ex-works are suitable
for altitudes upto 3,000 feet approximately. Carburetters used
constantly at altitudes 3,000 to 6,000 feet should have a reduction
in the main jet size of 5%, and thereafter for every 3,000 feet
in excess of 6,000 feet altitude, further reductions of 4% should
be made. |
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